Former vice president Joe Biden cruised to a 16-point victory in the crucial Michigan primary tonight, also winning Idaho, Mississippi, and Missouri. While results in Washington state are still too close call, Vermont senator Bernie Sanders won the North Dakota caucus.

Written off by many after a disastrous start to his 2020 presidential campaign, Biden defied the odds with an historic comeback which began a week-and-a-half ago in South Carolina, and continued throughout last week’s Super Tuesday states.

Heading into today’s contests—nicknamed “Super Tuesday II”—Biden led Sanders 670 delegates to 574; tonight’s final vote tallies will add more than 150 delegates to Biden’s total. In all, 1,991 are needed to clinch the Democratic presidential nomination

Biden has also capitalized on a number of endorsements by former presidential contenders, beginning last week with Minnesota senator Amy Klobuchar, former Texas congressman Robert “Beto” O’Rourke, South Bend, Indiana mayor Pete Buttigieg, and former New York mayor Mike Bloomberg. This week, he received endorsements from California senator Kamala Harris, New Jersey senator Cory Booker, and businessman Andrew Yang, also one-time presidential rivals.

Clearly, this is all bad news for Sanders. Although he began the campaign in a position of strength—focusing on his progressive agenda while letting others fight it out to be the centrist standard-bearer—the reduction of the field to a two-man battle has greatly changed the dynamic of the race. And while Michigan buoyed the Vermont senator's hopes in 2016 after an upset victory over Hillary Clinton, tonight's crushing loss in the Great Lakes State could serve as a cautionary tale: polling indicates that white male voters who chose Sanders over Clinton four years ago have now switched their allegiance to Biden.

While the door to a potential Sanders victory appears to be quickly closing, it should be noted that there are still another 17 primaries—and more than 1,500 delegates at stake—before the end of April. And with financial upheaval on Wall Street and the spread of the novel coronavirus, this remains a very volatile presidential race.

The viral outbreak has just begun to affect presidential campaigns, with both Biden and Sanders cancelling large rallies in Cleveland, Ohio tonight. This is likely just the first public safety step for a political process which thrives on large crowds, rope lines, and hands-on contact. While a return to the ‘front porch’ campaigns of the late 1800s is unlikely, candidates will undoubtedly modify the way they campaign, and quickly.

Next Tuesday, March 17th, four more states go to the polls: Arizona, Florida, Illinois, and Ohio—in all, an additional 577 delegates will be awarded.